1. Field of the Invention
The present invention relates to a character generator which utilizes font cartridges detachably loaded thereinto.
2. Description of the Prior Art
A character generator reads character pattern data in a font by accessing a font memory according to a character code instructed by a host machine such as a host computer, and sends the character pattern data to an output apparatus such as a printer.
In a character generator of this kind, it is desirable that a variety of fonts such as a font for small or large size characters and/or a font having a lot of characters is available in order to satisfy a variety of requirements by users.
Some character generators adopt a system in which a variety of the font cartridges having font memories is loaded. A font cartridge is one of external memories, and it stores data of character patterns included in one or more fonts.
Information data defining attributes of a font such as a capacity thereof, a kind thereof and so on stored in a font cartridge are stored in an area of memory means of the cartridge specified by predetermined addresses (Hereinafter, these information data on a font or a font cartridge are referred to as global information.) A microprocessor (CPU) for controlling the character generator identifies each cartridge by reading global information stored in said area.
As far as a conventional font cartridge is concerned, only one kind of font is stored in one font cartridge. Therefore, the global information of each of the font cartridges leaded is stored in an area having the same addresses as those of other font cartridges. Accordingly, the CPU identifies a font cartridge loaded by reading the data stored in the same area for each of them, and the kind and the characters of fonts stored in the font cartridges can be managed by accessing the addresses for every cartridge.
If the number of font cartridges to be loaded in a character generator is limited to a small number, it is desirable to store a plurality of kind of fonts in one font cartridge in order to generate many kinds of font at the same time.
In such a case wherein a plurality of kind of font is stored in a font chartridge, the CPU of a character generator should identify all of fonts stored in the respective font cartridges loaded. It is also desirable that the management by the CPU allows the capacity of font data and the number of fonts to be set freely.